Hollow-metal propeller



June 17, 1930. B. 5. BERG 1,764,927

HOLLOW METAL PROPELLER Filed July 21, 1928 i Bk Kiw TTOP Patented June 17, 1930 PA TE NT OFFICE BENGT EMIL BERG, F CHARLOTTE, NORTH CAROLINA HOLLOW-METAL PROPELLER,

Application filed July 21, 1928. Serial N'o. 294,443.

This invention relates to improvements in hollow metal propellers adapted primarily for use in aviation service. One object is to provide a propeller of this type that is 6 light in weight and flexible and at the same time of great strength. and of maximum durability in use.

With the foregoing and other objects in view the invention consists in the combination and arrangement of parts to be heretion.

Fig. 2 is a side view of Fig. 1'.

Fig. 3 is a cross section on line 33 of Fig. 1.

Fig. 4 is an enlarged View of the propeller rib employed.

Like reference characters denote oorre-,

sponding parts throughout the several views.

The shell of'the propeller is made preferably of metal rolled very thin, the shell being oftwo part formation, the parts be-- ing preferably welded together, the hub of the propeller having welded thereto the ends of two ribs that are welded also to the shell sections, the ribs being formed with elongated perforations connected by relatively narrow perforations thus providing a rib construction that is at once light in weight, exceedingly flexible and very strong and durable and that lends great strength to the shell. I I

The shell of the propeller is of the usual long and narrow shape with the ends rounded and comprises the front plate 1 that is flat and to which the rear plate 2 is secured, the rear plate being of an irreg-' ular convex form, the plate 2 rising abruptly from one edge of the plate 1 and being rounded and then tapering off gradually to receive the propeller shaft. Extending longitudinally and centrally of the propeller shell are the twin ribs 5, the'adjacent ends of which are welded to the hub. Each rib is formed of a single piece of material with its wide end- 6 welded to the hub, the rib tapering gradually toward its narrow end 7. The ribs are welded tothe plate 1 before the plate 2 is welded thereto and spot welded thereto at spaced intervals, the plate 2 being formed with a pluralit of perforations to permit it to be spot we ded to the rib after it is applied-to the plate 1.

Each rib 5 is, formed with a plurality of elongated perforations 8 that extend longitudinally of the rib from its larger end, said perforations being successively smaller and narrower and connected together by the slots 9. The perforations 8 reduce the weight of the rib to the minimum and the slots 9 provide maximum flexibility.

What is claimed is In a hollow metal propeller, a shell comprising front and rear plates, one of said plates being flat, the other plate being con vex and rising abruptly from one vlateral edge of said fiat plate and then tapering gradually to the opposite lateral edge, said plates having their meeting edges welded together, a hub connecting said plates and being welded thereto, and a pair of twin tapered ribs extending 1o gitudinally of said lates upon opposite sid s of said hub and eing welded thereto and to said plates, said ribs lying in a common plane and being formed with elongated spaced perforations,

said perforations successively becoming narrower as they recede from the larger ends of said ribs, said perforations being connected by narrow slots.

In testimony that I claim the foregoing as my own I have hereto afiixed my signature.

BENGT EMIL BERG.

the opposite edge of said plate, the meeting edges of the plates being preferably welde to ether. v

he hub 3 is welded to the plates 1, 2 and is formed with the central perforation 4 to 

